Method of processing waste water, in particular from malt factories and breweries

ABSTRACT

There is described a method of processing waste water, in particular from malt factories and breweries, which in the operational use is contaminated with microorganisms, salts and organic compounds. To enable a reuse, it is proposed to subject the waste water to a reverse osmosis after a treatment with activated sludge, before it is recirculated to the operational use.

This application is the national stage of PCT/IB98/00564 filed Apr. 2,1998.

This invention relates to a method of processing waste water, inparticular from malt factories and breweries, which in operational useis contaminated with microorganisms, salts and organic compounds.

As investigations concerning influences on the beer quality have shown,microorganisms introduced with the malt and their spores, above all thechlamydospore fungus fusarium, nickel and iron ions in conjunction withisohumulon as well as calcium oxalate severely impair the beer quality.To minimize the risk of such contaminations of the malt, drinking wateris used for soaking the barley grains for the process of germination,which drinking water is contaminated with microorganisms, salts andorganic compounds after the barley grains have started to germinate, andis discharged as waste water. Therefore, malting involves a great demandof drinking water, which can no longer be utilized after the operationaluse.

It is therefore the object underlying the invention to process wastewater, in particular from malt factories and breweries, as describedabove such that it can be utilized again.

This object is solved by the invention in that after a treatment withactivated sludge the waste water is subjected to a reverse osmosis,before it is recirculated to the operational use.

By combining a biological treatment of the waste water with a subsequentreverse osmosis, the waste water can surprisingly be cleaned from allcontaminants, and drinking-water quality can be achieved, so that thecleaned waste water can be recirculated to the operational use withouthaving to fear a malt contamination impairing the future beer quality,which malt is recovered from barley grains by means of a steep watercleaned in this way. After a biological decomposition of the organiccontaminants of the waste water, the remaining microorganisms, dissolvedmolecules and salts can be separated therefrom by means of a reverseosmosis, where the residue is discharged continuously and the permeatecan be utilized as pure steep water with drinking-water quality. Sincedue to the reverse osmosis the steep water is additionally decalcified,there is even obtained the advantage of an increase in qualityachievable thereby as compared to fresh drinking water. Although thedescribed processing of the waste water involves particular advantagesfor malting, it is of course not restricted to this field of applicationand can be used whereever waste waters and/or rinsing waters must beexpected, which are contaminated with microorganisms, salts and organiccompounds, as this may be the case with waste waters e.g. from the foodor beverage industry.

When the waste water to be cleaned also includes flocculatingsubstances, it is recommended to subject the waste water to aprecipitation preferably with iron(III) chloride as precipitating agent,after it has been reacted with activated sludge. Together with othersolids present, possibly after a sedimentation, the precipitatedsubstances can then be separated by means of a filter, before theprecleaned waste water is supplied to the reverse osmosis. By means ofthis prefiltration an unnecessary membrane contamination during thereverse osmosis can be avoided.

The waste water cleaned in this way need, however, not be supplieddirectly to the operational use. It may undergo a temporary storage insuitable containers. To be able to exclude a microbial contamination ofthe cleaned waste water during the temporary storage, the waste watercan be sterilized after it has been cleaned, for instance by means of aUV radiation or an ozone treatment.

FIG. 1 shows the invention.

The method in accordance with the invention will be explained in detailwith reference to the drawing, which shows a plant for performing aninventive processing of waste water in a simplified block circuitdiagram.

The drinking water used in a plant 1 for instance for germinating barleygrains in a malt factory, which drinking water is supplied to the plant1 via a supply line 2, is contaminated in this operational use withmicroorganisms, organic compounds and dissolved salts, which in the caseof conventional plants of this kind results in the waste water beingdischarged into the sewage system. To enable a processing of the wastewater suitable for a recirculation of the water via the plant 1, thewaste water is first of all supplied to a reactor 3, in which theorganic contaminants of the waste water are decomposed biologically. Forthis purpose, the reactor 3 includes an activated sludge, which is firstof all supplied with oxygen through an intensive aeration, before thecontrol program effects a change from the aerobic to the anoxic phase,in order to eliminate both nitrogen compounds and phosphates. Thesedecomposition phases are followed by a sedimentation phase, in which thebacterial floccules settle down, so that the supernatant, biologicallyprecleaned waste water can be withdrawn and be supplied to a subsequentprecipitation tank 4.

The reactor 3 then is available for the biological treatment of afurther waste water batch. The aeration of the individual batches, thedenitrification, the sedimentation of the biomass as well as themonitoring of the temperature, the pH value, the oxygen content and thelike can largely be controlled automatically. The excess sludge obtainedin the reactor 3 is pumped off into a stacking tank 5, where afterseveral days of an aerobic sludge stabilization it is thickened by meansof a further aeration and addition of a flocculating agent, in order tothen either be disposed of in a communal sewage disposal plant or bereused in agriculture.

In the precipitation tank 4, residual impurities can be flocculated inorder to reduce the chemical oxygen demand, namely be means of aprecipitating agent supplied via line 6. Iron(III) chloride isparticularly useful, by means of which e.g. phosphates can also beeliminated chemically. After the precipitation, the waste water from theprecipitation tank 4 is supplied to a filter stage 7, in which thesolids still present are retained. This filter stage 7 preferablyconsists of at least one cloth or gravel filter with a size ofseparation of 1 to 20 μm, preferably 5 to 10 μm or a micro- orultrafiltration stage with a size of separation of 0.005 to 5 μmpreferably 0.05 to 1 μm. By means of a turbidity meter, thecontamination of the filter stage 7 can be monitored.

The waste water precleaned in this way is then subjected to a reverseosmosis in a filter stage 8, where by means of an appropriate choice ofthe membranes the existing microorganisms, dissolved molecules and saltsare separated. The residue is discharged continuously and after a finalinspection supplied to the sewer via a discharge line 9. When the outletvalues required for an introduction into the sewer are not reached, theresidue can be recirculated to the reactor 3 via the return line 10.

The permeate has drinking-water quality and can be recirculated to theoperational plant 1 via the cycle line 11. In accordance with theillustrated embodiment, there is provided a temporary storage in astorage tank 12, which is connected to a sterilization stage 13, so thatthe risk of a renewed microbial contamination can be excluded. Thissterilization stage 13 may comprise an UV radiation or an ozonetreatment.

Due to the recirculation of a large part of the water used in the plant1 for operational purposes a considerable saving of fresh water isachieved, where the additional advantage of a decalcination of therecirculated water is obtained. Fresh water supplied via the supply line2 is merely required to compensate the waste water losses.

From a plant 1 of a malt factory waste water was obtained in anexperiment, which waste water had a chemical oxygen demand of 1410 mg/land a biochemical oxygen demand based on 5 days of 730 mg/l. The pHvalue was 7.5. In addition, contaminations by 23 mg/l ammonium, 22 mg/lnitrates, 1200 mg/l chlorides, 8.35 mg/l phosphates and 31 mg/l sulfatescould be detected. By reacting the waste water with activated sludge inthe reactor 3, the chemical oxygen demand could be decreased to 44 mg/l,and the biochemical oxygen demand could be decreased to 9 mg/l. Thecontent of ammonium was reduced to 16 mg/l, the chloride content to 647mg/l, and the phosphate content to 4.57 mg/l. The nitrate content was123 mg/l, and the nitrite content was 40.2 mg/l.

After a precipitation with iron(III) chloride and a prefiltration at asize of separation of 15 μm, the waste water having a chemical oxygendemand of 100 mg/l, a pH value of 7.2, an electrical conductance ofabout 6000 μS/cm, a potassium content of 165 mg/l, an ammonium contentof 5 mg/l, a nitrite content of 1 mg/l, a nitrate content of 100 mg/l, achloride content of 1000 mg/l and a phosphate content of 10 mg/l couldbe subjected to the reverse osmosis. The amount of permeate was 22.5m³/h. The chemical oxygen demand of the permeate was in the rangebetween 5 and 10 mg/l. At a pH value of 6.9 the electrical conductancewas 541 μS/cm. As residual contaminations 12 mg/l could be detected forpotassium, 10 mg/l for nitrates and 100 mg/l for chlorides. The residualcontent of ammonium, nitrites and phosphates was below the limit ofmeasurement. As microbial counts there were detected threecolony-forming units/ml for bacteria at 20° C. and eleven colony-formingunits/ml for bacteria at 36° C. In 100 ml each of the cleaned wastewater no coliform microbes, no coli bacteria and no fecal streptococcias well as clostridia could be detected.

What is claimed is:
 1. A method of processing industrial waste watercontaminated with microorganisms, salts and organic compounds in a maltfactory or brewery, comprising the steps of (a) treating thecontaminated industrial waste water with activated sludge, (b)pre-cleaning the treated product by subjecting the same to aprecipitation, (c) subsequently subjecting the pre-cleaned product to areverse osmosis, and (d) recirculating the product of the reverseosmosis to the operational factory stage.
 2. The method of claim 1,comprising the further steps of temporarily storing the product of thereverse osmosis and sterilizing the same before recirculating it to themalt factory or brewery.
 3. The method of claim 1, wherein the treatedproduct is subject to a precipitation with iron (III) chloride.
 4. Themethod of claim 1, comprising the further step of pre-filtering thepre-cleaned product prior to subjecting it to the reverse osmosis.